This invention relates to improvement in pipetting devices.
Many proposals have been made to provide pipetting devices of various constructions which can be used conveniently to transfer a desired amount of liquid samples rapidly and accurately. Examples of devices of this type can be found in U.S. Pat. Nos. 2,798,647, 3,494,201, 3,810,391, 3,827,305, and 3,855,867. Typically, such pipetting devices includes a cylinder disposed at the lower end portion of a tubular housing coaxially therewith, a piston reciprocably fitted in the cylinder and having an actuating rod connected thereto to extend coaxially in the tubular housing, an actuating knob secured to the upper end of the actuating rod, a discharge nozzle connected to the lower end of the cylinder, and a return spring biasing the actuating rod or the piston in the upward direction. Naturally, there is disposed, further, means for adjusting the stroke of the piston and means for indicating the amount of liquid dischargeable in respective adjusted conditions.
However, there are shortcomings in prior art pipetting devices such that the construction of piston stroke adjusting means and/or indicating means is complicated very much so that the adjusting procedure is troublesome and time consuming and the manufacturing cost is expensive, and that accurate adjustment can not be achieved as in the case when graduations are marked on the wall of the glass cylinder and the sealing surface of the piston serves as the datum line, and that the pipetting device can not be used in two appliances, namely, one for sucking a liquid sample from one container, moving the device upon the other container and discharging the sample into the other container, and one for sucking a liquid sample from one container located at a position remote from the device and discharging the sample without moving the device.